When a picture is taken by a camera, the film exposure should be determined beforehand. But it is sometimes difficult to determine the most desirable exposure value for a given picture scene. It is useful in this case to determine the most desirable exposure factors such as shutter speed and diaphragm aperture value among a plurality of pictures taken by the bracket photographing function.
Normally, no flash light is used in bracket photographing. But if flash light is used in bracket photographing, the aperture value, rather than the shutter speed, should be changed to change the exposure value because the duration of a flash light emission should be within synchronizable shutter speed when a focal plane shutter is used. One of the problems in this case is that the depth of field changes between frames which may be against the photographer's intention. Another problem arises when a rather sophisticated camera system is used in which a camera computer controls the light emitting amount of the flash light unit attached to the camera. In this camera system, the camera computer stops flash light emission when the amount of light received through the photographic lens reaches a preset value. Therefore, when the aperture value of the photographic lens is changed to reduce the incoming light amount, the camera computer automatically compensates for the reduction by elongating the duration of the flashing to keep the exposure value of the main object (on which the flash light is most effectively given) constant. This means that a flash bracket photographing by changing the aperture value is nonsense in such a camera system.